Dynamo electric machines and stators for use in same

ABSTRACT

Dynamo electric machines and stators for use in such machines are provided. The stators comprise plates configured to be substantially flat and a plurality of spaced apart projections or teeth extending away from the plate and, together with the plate defining a plurality of slots therebetween. The stators comprise masses of metal particles. Using stators made from such metal particles provides enhanced machine efficiency, which is believed to be because of reduced eddy current effects in the stator. Motors including rotors having generally flat arrays of permanent magnetic poles and such stators which are spaced apart from and generally facing the permanent magnetic poles and have a plurality of magnetic windings, and pumps powered by such motors are included within the scope of the present invention.

The present application is a continuation of application Ser. No.09/533,320, filed Mar. 22, 2000, now U.S. Pat. No. 6,347,929; which is acontinuation of application Ser. No. 08/906,847, filed Aug. 6, 1997, nowU.S. Pat. No. 6,132,186. The disclosure of each of these applications isincorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to dynamo electric machines and statorsfor use in same. More particularly, the invention relates to generallyflat structured, dynamo electric machines, e.g., brushless electricmotors, and to stators for use therein.

Brushless electric motors have been suggested and/or used for variouspurposes. In general, such motors come in at least two configurations; adrum style motor in which the rotor and stator of the motor havegenerally cylindrical shapes; and a flat style motor in which the rotorand stator of the motor are present as generally flat discs. Althoughthe drum style motors are often capable of generating more power, theflat style motors have the advantage of being compact in size.

It would be advantageous to provide flat style or disc brushlesselectric motors which generate increased amounts of power.

Flat style brushless electric motors have been suggested for use withimpeller pumps. See, for example, Mizobuchi et al U.S. Pat. No.4,806,080; Kricker et al U.S. Pat. No. 5,332,374; and Atsumi U.S. Pat.No. 5,407,331. There continues to be a need to provide new impellerpumps driven by powerful flat style brushless electric pumps, inparticular for pumping liquids, such as water and the like.

SUMMARY OF THE INVENTION

New dynamo electric machines, stators for use in such machines and pumpsincluding such stators have been discovered. The present invention takesadvantage of the discovery that dynamo electric machine statorscomprising masses of metal particles, preferably pressed metalparticles, provide more efficient, powerful dynamo electric machines,preferably brushless electric motors having longer useful lives and/orproducing increased or enhanced amounts of power, relative to similarmachines having substantially the same dimensions and including statorsmade from solid metal members.

Without wishing to limit the invention to any particular theory ofoperation, it is believed that the present stators which comprise massesof metal particles are effective in disrupting, or otherwise mitigatingagainst the harmful effects of, eddy currents that develop in thestator. Such eddy currents reduce the effectiveness of the dynamoelectric machines, for example, the effective power generating abilityof the brushless electric motor. In any event, the present dynamoelectric machines, including stators comprising masses of metalparticles, have been found to be powerful and effective in manyapplications.

The present stators are useful in any dynamo electric machines, forexample, motors, generators, alternators, motor/generator combinations,motor/tachometer combinations, frequency changers and the like.Preferably the dynamo electric machine is of the brushless type, andmore preferably of the brushless direct current (DC) type. The term“motor” is used extensively hereinafter and is meant to encompass orinclude within its scope any such dynamo electric machine.

One particularly useful application of such stators is in brushlesselectric motors which power work components, such as pump and compressorimpellers, fan blades, mixing and blending implements and the like. Avery advantageous configuration provides such stators used incombination with rotors which are integral with the work component.Pumps, such as liquid handling pumps, powered by such brushless electricmotors are very beneficial embodiments of the apparatus of the presentinvention.

The present motors, stators, apparatus and pumps are relativelystraightforward in construction and easy to use. These motors, stators,apparatus and pumps provide a high degree of reliability and longeffective life and provide one or more advantages which enhanceperformance and/or cost effectiveness.

In one embodiment, the present invention is directed to motors (dynamoelectric machines), preferably brushless electric motors, which comprisea rotor and a stator. The rotor has a rotary axis and includes aplurality of permanent magnetic poles arranged in a generally flatarray. The stator, which comprises a mass of metal particles, preferablya mass of pressed metal particles, is spaced apart from and generallyfacing the generally flat array of permanent magnetic poles. The statorhas a plurality of magnetic windings positioned and adapted to effectrotation of the rotor about the rotary axis upon energization thereof.

Reduced eddy currents preferably are obtained during operation of suchmotors relative to the operation of similar motors in which the statorcomprises a solid metal mass or member instead of the mass of pressedmetal particles. In addition, when compared to stator bodies made solelyof polymeric materials, the present stator bodies provide motors withreduced effective air gaps between the stators and the rotors, whichfeature ultimately yields more powerful motors relative to similarmotors with stator bodies of polymeric materials. The present statorspreferably consist essentially of a mass of pressed metal particles. Themass of pressed metal particles advantageously has a density equal to atleast about 95% of the theoretical density of a solid metal member. In avery useful embodiment, the stator includes substantially linearacicular metal particles having a substantially triangularconfiguration.

The present motors preferably are brushless direct current (DC) electricmotors, for example, brushless DC, one (1), two (2) or more, such asthree (3), phase electric motors.

The present stators preferably comprise plates, for example,substantially flat plates, and a plurality of spaced apart projectionsor teeth including masses of metal particles, for example, as describedherein. The plates of the present stators have a first end surface, asubstantially opposing second end surface and a peripheral surfacetherebetween. The plurality of spaced apart projections extend from thesecond end surface away from the plate and, together with the second endsurface of the plate, define a plurality of slots therebetween.

The plate preferably has a central axis which intersects both the firstend surface and the second end surface. Each of the plurality ofprojections preferably extends inwardly from the peripheral surface andterminates prior to intercepting the central axis.

Each slot of the plurality of slots preferably has a substantiallyconstant dimension between the two adjacent projections which define theslot. In a very useful embodiment, the plate and projections areunitary, that is are made of a single or unitary member.

Apparatus for performing useful work are provided which comprise workcomponents, rotors and stators. The work components, such as pump orcompressor impellers, fan blades, mixing and blending implements, othersassemblies which perform useful work on a material in contact with thework component and the like, include a rotary axis and are mounted forrotation about the rotary axis. The work component is configured andpositioned so that the rotation of the work component is effective toperform work on a material in contact with the work component. The rotoris coupled, preferably directly coupled, to and rotatable with the workcomponent and includes a plurality of permanent magnetic poles arrangedin a generally flat array. The stator is as described previously and isadapted to effect rotation of the rotor and the work component uponenergization thereof.

As used herein, the term “directly coupled” as it relates to therelationship between the work component and the rotor refers to anapparatus in which the work component and the rotor are directly securedor attached to each other, so that no power transmission assembly, forexample, a shaft, gear arrangement or the like, transfers power from therotor to the work component. This “direct coupling” relationship, whichmay be considered an integral rotor/working component combination, veryeffectively provides power to the work component while reducing the sizeand space requirements of the apparatus.

In a very useful embodiment, the work component and stator are presentin a unitary or single member, for example, a member made of asubstantially uniform composition.

Pumps are provided which comprise pump casings, impellers, rotors andstators. The pump casing has an inlet and an outlet. The impeller has arotary axis and rotatably mounted within the pump casing for rotationabout the rotary axis. The impeller is configured and positionedrelative to the pump casing so that rotation of the impeller iseffective to urge fluid from the inlet to flow through the outlet. Therotor is coupled to and rotatable with the impeller and includes aplurality of permanent magnetic poles arranged in a generally flatarray. The stator is as described previously and is adapted to effectrotation of the rotor and the impeller upon energization thereof.

The present work apparatus and pumps preferably provide increased orenhanced power, and more preferably reduced detrimental eddy currenteffects, during operation relative to similar apparatus and pumps inwhich a solid metal mass or member is used in place of the mass of metalparticles in the stator.

Each of the features disclosed herein is included within the scope ofthe present invention. In addition, all combinations of the presentlydisclosed features which are not mutually inconsistent or incompatibleare also included within the scope of the present invention.

These and other aspects and advantages of the present invention areapparent in the following detailed description and claims, particularlywhen considered in conjunction with the accompanying drawings in whichlike parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective drawing of a stator in accordance with thepresent invention.

FIG. 2 is a front plan view of the stator shown in FIG. 1.

FIG. 3 is a perspective drawing of an alternate embodiment of a statorin accordance with the present invention.

FIG. 4 is a front plan view of the stator shown in FIG. 3.

FIG. 5 is a perspective view of a metal particle used in forming thestators shown in FIGS. 1 to 4.

FIG. 6 is a perspective drawing of a fully assembled pump in accordancewith the present invention.

FIG. 7 is a perspective view of the pump shown in FIG. 6 with the partsexploded for illustrative clarity.

FIG. 8 is a cross-sectional view taken generally along line 8—8 of FIG.6.

FIG. 9 is a cross-sectional view taken generally along line 9—9 of FIG.8.

FIG. 10 is a front plan view of the rotor of the pump shown in FIG. 7.

FIG. 11 is an enlarged partial cross-sectional view of the central areaof the pump shown in FIG. 6 emphasizing the space between the stator androtor.

FIG. 12 is a cross-sectional view taken generally along line 12—12 ofFIG. 11.

FIGS. 13A, 13B and 13C are front plan views of the stator of the pumpshown in FIG. 7 illustrating a windings pattern for a six (6) pole,three (3) phase motor.

FIGS. 14A, 14B and 14C are front plan views of the stator shown in FIGS.3 and 4 illustrating a windings pattern for a six (6) pole, three (3)phase motor.

FIG. 15 is a schematic illustration, side section, of an alternateembodiment of a motor in accordance with the present invention.

FIG. 16 is another schematic illustration, top view, of the embodimentshown in FIG. 15.

FIG. 17 is a schematic illustration, side section, of an furtherembodiment of a motor in accordance with the present invention.

FIG. 18 is another schematic illustration, top view, of the embodimentshown in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, a stator, shown generally at 10, inaccordance with the present invention includes a substantially flatplate 12 having a back surface 14, a substantially opposing frontsurface 16 and a peripheral surface 18 therebetween. Extending from thesubstantially flat front surface 16 and peripheral surface 18 are aseries of nine (9) projections which extend away from the front surfaceand radially inwardly from the peripheral surface and terminate prior tothe central axis 22 of the stator 10.

Each of the projections 20 includes a outer peripheral surface 24, aninner peripheral surface 26 and two (2) equally sized side surfaces 28.The side surfaces 28 between adjacent projections 20, together withfront surface 16, form a slot 30. Each of the slots 30 is equally sizedand has a substantially constant dimension radially inwardly from theperipheral surface 12 and outer peripheral surface 24. A series of three(3) notches 32 are located on three (3) adjacent projections 20 ofstator 10. Each of these notches 32 is adapted to receive and hold aHall sensor. These Hall sensors are useful in controlling the operationof the motor including stator 10.

Stator 10 is particularly effective for use in a three (3) phase directcurrent (DC) brushless electric motor. However, stators similar incomposition to stator 10 can be employed in one (1), two (2) or morephase DC brushless electric motors. Electric windings are provided inthe slots 30. One pattern for such windings is illustrated in FIGS. 13a,13 b and 13 c. For the sake of clarity, only one winding is shown ineach of FIGS. 13a, 13 b and 13 c (and also in FIGS. 14a, 14 b and 14 c).However, a relatively large number of windings preferably are includedin each of the slots 30, and the number of windings is chosen based onthe desired power output of the motor.

An important feature of the present stator 10 is that it is made from amass of metal particles. Specifically, stator 10 is made from a mass ofpressed metal particles. Such particles of metal, for example, metalshaving magnetic properties, i.e., metals which are attracted to magnets,such as iron, nickel, cobalt, other magnetic metals and the like,alloys, such as steel, iron and/or other metal or metals having magneticproperties alloyed with molybdenum, manganese, chromium, carbon, sulfur,silicone, copper, nickel, vanadium, niobium, gold, aluminum, phosphorusand the like and mixtures thereof, preferably are substantially linear,acicular particles having a substantially triangular configuration. Sucha particle, shown generally at 34, is illustrated in FIG. 5.

Stator 10 may be, and preferably is, prepared in accordance with Krauseet al U.S. Pat. No. 5,594,186, the disclosure of which is incorporatedin its entirety herein by reference.

The metal particles 34 preferably have dimensions of about 0.002 toabout 0.05 inches in height (H dimension in FIG. 5), about 0.002 toabout 0.05 inches along the base (B dimension in FIG. 5) and about 0.006to about 0.20 inches in length (L dimension in FIG. 5). The metalparticles preferably have a substantially triangular cross-section and adie fill ratio of less than 3 to 1, with sufficient particle flowcharacteristics to permit the economic manufacture of the stator havinga density of at least about 95%, and more preferably at least about 96%,of the theoretical density of a solid metal member.

It should be noted that the metal particles which may be used to producethe present stators can be of any suitable size, shape andconfiguration. Such particles preferably are of such configuration thata flat style motor, as described herein, including a stator made from amass of such particles provides for increased power production and/orreduced detrimental eddy current effects relative to a similar motor inwhich the stator is made from a mass of solid metal rather than the massof such particles. Also, the metal particles having a substantiallytriangular cross-section useful in the present invention are not limitedto the embodiment shown in FIG. 5. Such metal particles can havelongitudinal surfaces that are independently convex, concave and/orplanar.

In addition, the present stators can be made in the form of a compositein which the mass of metal particles is combined, e.g., layered, mixedor otherwise composited, with one or more other materials, for example,polymeric materials, wood and the like and mixtures thereof. Such acomposite stator should include a sufficient amount of the metalparticles to function effectively as a stator and to provide at leastone of the benefits or advantages described herein. Such compositestators can be produced using conventional composite productiontechniques, for example, mixing, layering, compressing, shaping,injection molding, etc.

The stator 10 of the present invention may be prepared by thetraditional metal powder process comprising the steps of: (1) forming ametal particle mixture comprising the metal particles and a lubricant;(2) cold uniaxial pressing of the mixture to form a green compact havinga high green density and good green strength; (3) heating the greencompact at a sufficient temperature to pyrolyze the lubricant and formthe metal stator; (4) optionally sintering the stator at a sufficienttemperature for a sufficient time to impart additional strength to thestator and form a sintered stator; and (5) cooling the stator orsintered stator, then performing optional secondary operations on thestator to provide a finished metal component. Preferably, the methodcomprises a single cold, uniaxial pressing step, a single heating step,and a single sintering step, and provides a green compact and a statorhaving a density at least 95%, and preferably at least 96%, of thetheoretical density, and a finished stator of essentially the identicalsize and shape of the green compact.

The lubricant used is typically an organic compound having a density ofabout 0.8 to about 1 g/cc (gram per cubic centimeter). In contrast, thepowdered metal typically has a density of about 6 to about 8 g/cc.Accordingly, on a volume basis, even a small amount of lubricant byweight occupies an appreciable portion of the die volume. To achieve ahigh density, the volume occupied by lubricant preferably is minimized.Therefore, the lubricant preferably is present in an amount of about0.015% to about 0.4% and more preferably about 0.015% to about 0.25%, byweight of the metal particle mixture.

The lubricant is an organic compound capable of being decomposed, orpyrolyzed, at the heating temperature. The pyrolysis products are gaseswhich are expelled during heating. The lubricant may be a solid at roomtemperature and incorporated into the metal particle mixture inparticulate form. Examples of lubricants include, but are not limitedto, ethylene bis-stearamide, C₁₂ to C₂₀ fatty acids, for example,stearic acid and the like, paraffins, synthetic and/or natural waxes,polyethylene, fatty diesters, fatty diamides and the like and mixturesthereof. Salts of organic acids, like zinc, lithium, nickel, iron,copper, and/or magnesium stearate, also can be used as the lubricant.However, acid salt lubricants can leave a metal oxide by-product in thefinished stator. The metal oxide by-product can adversely effect thestator.

For additional details regarding the production of stator 10 see theabove-noted Krause et al patent.

FIGS. 3 and 4 show a substantially similar stator, shown generally at40, which is substantially similar to stator 10. Components of stator 40which correspond to components of stator 10 are identified by the samereference numeral increased by 30.

The primary difference between stator 40 and stator 10 is in the numberand size of projections 50 relative to projections 20. Specifically,stator 40 has eighteen (18) projections 50 as opposed to nine (9)projections 20. Each of the projections 50 is substantially smaller insize than the projections 20.

Stator 40 can be employed in a three (3) phase electric motor in whichelectric windings are provided within the slots 60 of the stator, usinga winding pattern as shown in FIGS. 14a, 14 b and 14 c. Of course, astator structured similarly to stator 40 can be used in a one (1), two(2) or more phase DC brushless electric motor.

In the following description, the stator 10 is used. However, it shouldbe noted that stator 40 can be similarly used.

A motor/work component in accordance with the present invention isillustrated as follows. A motor/pump combination, shown generally at110, includes a housing 112 which is made up of a pump cover 114, a pumpcase 116, a bulkhead housing element 118, a stator housing 120, acontrol housing 122 and a control cover 124. These housing components ofcombination 110 are fastened together using a plurality of conventionalscrew-type fasteners 126 which pass through each of the housingcomponents from pump cover 114 to control cover 124. Conventionalfastener nuts 127 are coupled to the fasteners 126 to maintain thefasteners in place.

Pump cover 114 includes a liquid inlet 130, while pump case 116 includesa liquid outlet 132. An impeller 134, a rotor 136 and stator 10(including magnetic windings which are not shown) are positioned in theassembled combination 110, as shown in FIG. 8. The bulkhead housingelement 118 carries a bulkhead sheet 138 which includes a centrallylocated boss 140. The combination of bulkhead housing element 118 andbulkhead sheet 138 is an integrally formed structure and forms a staticseal which prevents the stator 10 from being exposed to the liquid beingpumped. Stator 10 is disposed in stator housing 120. Control housing 122houses the controls for the operation or activation of the stator 10.

As shown in FIG. 8, centrally located boss 140 is configured to supportstationary axle 144, which is of tubular (hollow or solid) construction,at end 146. The boss 140 and/or end 146 of axle 144 are keyed or includeengaging flat surfaces which facilitate maintaining the axle stationaryrelative to the boss. Axle 144 extends beyond the bulkhead sheet 138into impeller 134 through the central opening 148 of annular rotor 136.

Impeller 134 includes an opening 152 which extends away from the inlet130 and is configured to allow both axle 144 and rotating bearing 154 tobe received therein. End 155 of axle 144 in opening 152 is free, that isit is not secured to impeller 134. In addition, a thrust bearing 156 ispositioned in the boss 140 and is maintained stationary. This thrustbearing 156 faces the back surface 158 (FIG. 8) of bearing 154 whichrotates with impeller 134 and rotor 136 around axle 144. Thrust bearing156 can be relatively small because the net thrust force is reducedsince the axial force from the rotor 136 opposes the force induced bypressure rise.

Annular rotor 136 includes a series of six (6) alternating permanentmagnetic poles 159, as shown in FIG. 10. Permanent magnetic poles 159,which are alternating north (N) and south (S) magnetic poles, arearranged in a circular array and are positioned to face the stator 10.In addition, rotor 136 includes an annular region 161 extending awayfrom stator 10 which has the magnetic properties of iron. Annular region161 is coextensive with the areas of permanent magnetic poles 159perpendicular to the rotary axis 170 of motor/pump combination 110.Region 161 with the magnetic properties of a soft magnetic material,such as iron, enhances the interaction between the stator 10 and rotor136, thereby enhancing the ability of the rotor 136 to be rotated inresponse to the magnetic windings located on stator 10 and enhancespower generation.

The rotor 136 can be made of individual magnetic segments to provide thepermanent magnetic poles and a region or layer (corresponding to region161) of iron located on the back side (away from stator 10) of the rotorto provide the magnetic properties of a soft magnetic material. Onealternative is to use a ring magnet, in place of the individual magnetsegments, to provide the plurality of permanent magnetic poles, togetherwith a back layer or region of iron and the like having magneticproperties of a soft magnetic material. However, rotor 136 preferably isan integral structure, for example, made of a composite of athermoplastic polymeric matrix material, such as polypropylene and thelike, and strontium ferrite and the like particles, which can bemagnetized to provide both the alternating permanent magnetic poles 159as well as an annular region 161 extending away from the stator 10 whichhas the magnetic properties of a soft magnetic material.

In producing such a composite rotor, the percentage of each constituentis adjusted in order to obtain the desired balance of magnetic andstructural properties. The composite rotor may be formed by an injectionmolding process in which the mixed constituents is heated to be flowableand then forced into a closed cavity mold. While the mixed material isstill in the mold, magnetizing apparatus, appropriately positionedrelative to the mold, is energized, thereby aligning the magneticparticles within the mixed material. In a preferred embodiment, ratherthan having flux lines that are perpendicular to the pole face as theypass through the rotor 136, the internal flux at the back region(corresponding to region 161) of the rotor is directed to turn parallelto the pole face surface and towards the adjacent opposite polaritypoles. Essentially, this creates a flux return path within the rotor 136and eliminates the need for a separate magnetic part (back iron).

The integrally structured rotor 136 described herein is an example of aring magnet with the additional feature that a region 161 (FIG. 7) ofthe structure is magnetized to have magnetic properties of a softmagnetic material. Having such an integral structure providessubstantial benefits. For example, reduced weight is achieved whichreduces pump wear and vibration. Also, the use of an integral rotor 136reduces the number of parts included in the combination 110.

Impeller 134 includes a series of curved vanes 160 which are present inthe primary liquid flow path between inlet 130 and outlet 132. Uponrotation of impeller 134, vanes 160 are effective to impart centrifugalenergy to the liquid passing through inlet 130 which urges the liquid toflow under increased pressure through outlet 132. Thus, impeller 34 andvanes 60 provide the primary pumping action in motor/pump combination110.

The impeller 134 is directly coupled to, that is integral with, therotor 136. Thus, impeller 134 rotates in direct response to the rotationof rotor 136 with no coupling or power transfer assembly, such as ashaft, gear arrangement and the like, between these two components. Thisdirect coupling feature reduces the size of combination 110 and thenumber of components required. In a very useful embodiment, impeller 134and rotor 136 are present as a single or unitary member. For example, asingle part structured or configured to include both impeller 134 androtor 136, for example, made from the composite material describedpreviously with regard to rotor 136, can be formed using conventionaltechniques and performs very effectively in accordance with the presentinvention. Such a unitary impeller 134/rotor 136 is shown in thedrawings simply by considering the impeller and rotor as a single part.The advantages provided by such a unitary impeller (work component)134/rotor 136 include size reduction, reduced member of components andease of assembly.

The maximum magnetic cross-sectional area of rotor 136 perpendicular torotary axis 170 of the pump 110 is larger than the maximumcross-sectional area of impeller 134 perpendicular to the axis. The useof a relatively large rotor 136 allows much shorter housing profiles,for example, relative to drum style brushless electric motor/pumpcombinations. In addition, the relatively large rotor 136 provides alarger area adjacent the bulkhead sheet 138 for dissipation of heat, forexample, into the liquid from inlet 130 (as is described hereinafter),thereby reducing or even eliminating the need for bypass coolingpassages. Further, the large rotor 136 provides the extra area neededfor the diffusion sections of the combination 110 so that there is lesswasted space. Moreover, the large rotor 136 relative to the impeller 134provides increased power to the impeller while, at the same time,reducing the weight of the impeller relative to the rotor. Sincerelatively less weight is being rotated, the combination 110 performsmore efficiently. In other words, more of the power that is generated bythe interaction between the stator 10 and the rotor 136 is passed to theliquid being pumped through outlet 132.

The stator 10 includes a plurality of magnetic windings 172 (see FIGS.13A, 13B and 13C) positioned to interact with the permanent magneticpoles 159 of the rotor 136 to effect rotation of the rotor and theimpeller 134 upon energization of the windings. The combination of rotor136, stator 10 (with windings 172) and controls in control housing 122forms a six (6) pole, three (3) phase brushless DC electric motorassembly. In this embodiment, the windings 172 on stator 10 can beprovided as illustrated in FIGS. 13A, 13B and 13C. Of course, thepresent invention is not limited to any specific number of permanentmagnetic poles or to a motor of any particular phase or phases. The discor flat arrangement of the present motors and motor/pump combinationallows substantial flexibility in terms of size, number of permanentmagnetic poles and motor configurations.

The controls included within control housing 122 act to control theoperation of the stator 10 so as to provide the desired rotation of therotor 136 and impeller 134. These controls can be based on electronicswhich are conventional and well known in the art. In particular,controls which are useful in operating brushless DC electric motors maybe employed. Since such controls are conventional and well known in theart, a detailed description thereof is not needed to practice thepresent invention and is, therefore, not presented here.

An increase in efficiency is achieved by reducing the running frictionof the motor/pump combination 110. This is accomplished, at least inpart, by using a portion of the liquid from inlet 130 to establish afluid film between the rotating rotor 136 and impeller 134 and thestationary frame, that is the bulkhead sheet 138, stator 10 andassociated components. This fluid film is provided as follows.

With particular reference to FIGS. 11 and 12, a portion of the liquidfrom inlet 130 passes into a fluid passageway 173 in impeller 134.Bearing 154 includes a series of four (4) fluid pathways 174 whichextend along the outer surface 176 of the axle 144 along the entirelength of the bearing 154. These fluid pathways 174 empty into the spacebetween the bulkhead sheet 138 and the back surface 178 of impeller 134.Further, back surface 178, as shown in FIG. 12, includes a series ofradially extending vanes 180 which are rotatable with the impeller 134and positioned to urge liquid from the fluid pathways 174 to flow intothe space 182 between the bulkhead sheet 138 and the impeller 134 androtor 136. This liquid forms a film which reduces friction between therotating and non-rotating components of motor/pump combination 110 andconducts heat caused by the rotation away from the site of the rotation,thereby facilitating more efficient operation of the combination. Theliquid is in fluid communication with the outlet 132 so that acontinuous flow of liquid is provided in the fluid pathways 174 and inthe space 182 between the impeller 134 and rotor 136 and the bulkheadsheet 138.

Bulkhead housing element 118 and bulkhead sheet 138 provide a sealbetween the rotating portion, e.g., rotor 136 and impeller 134, ofcombination 110 and the non-rotating or stationary portion, e.g., stator10, of the pump. Thus, no rotating member passes through the seal platedefined by bulkhead housing element 118 and bulkhead sheet 138. Thereare no moving parts within the stationary or electromagnetic portion,e.g. stator 10, of the combination 110. All the moving parts have beenintegrated into the rotating portion of combination 110. This integratedrotor design feature reduces wear and tear on pump 110 and avoidsexposing the stator 10 to the liquid being pumped.

Bulkhead sheet 138 which is positioned, has a configuration and/or ismade of material so as to provide one or more enhancements to motor/pumpcombination 110. Thus, bulkhead sheet 138 is positioned between therotor 136 and the stator 10 and includes one or more regions,particularly regions which directly face the rotor, which are in contactwith and structurally supported by the stator. Allowing the stator 10 tostructurally support at least a portion of the bulkhead sheet 138reduces the size of combination 110, and allows the use of a relativelythin film or layer of material as the bulkhead sheet. For example, theregion or regions of the bulkhead sheet 138 which are structurallysupported by the stator 10 are preferably less than about 30 mils thick.Having the bulkhead sheet 138 very thin allows for increased interactionbetween the windings 172 on the stator 10 and the permanent magneticpoles 159 on the rotor 136. This provides for increased efficiency inthe interaction between the stator 10 and rotor 136 and increased powergeneration.

Moreover, the bulkhead sheet 138, particularly the regions of thebulkhead sheet which directly face the rotor 136, are preferably made ofa material having a low magnetic permeability, to further reduce thedetrimental effects of eddy currents. The reduced magnetic permeabilityof bulkhead sheet 138 allows for increased interaction between thewindings 172 on the stator 10 and the magnetic poles 159 on the rotor136. The high coefficient of thermal conductivity allows foradvantageously increased dissipation of heat and, ultimately, increasedlife of motor/pump combination 110.

Because at least a portion of the bulkhead sheet 138 is structurallysupported by the stator 10, a wide range of materials, satisfying boththe reduced magnetic permeability and increased coefficient of thermalconductivity requirements, noted above, can be used in producing thebulkhead sheet. In other words, since the bulkhead sheet 138 is at leastpartially structurally supported by the stator 10, the strength of thematerial from which the bulkhead sheet is made is not a primary concern.Examples of useful materials for the bulkhead sheet 138 are brass,austenitic stainless steel, polymeric materials and the like.

Motor/pump combination 110 is constructed so that a very effectivestatic seal is provided by bulkhead sheet 138 so that no liquid frominlet 130 comes in contact with the stationary portion, e.g., stator 10,of the pump. The fact that a static seal, rather than a rotating orotherwise moving seal, is used reduces wear and tear and increases theeffective useful life of pump 110.

Components of housing 112 and impeller 134 can be produced usingpolymeric materials.

In another embodiment, shown schematically in FIGS. 15 and 16, abrushless DC electric motor, shown generally at 200, includes two (2)stators 210 and a rotor 236 therebetween. The rotor 236 is secured tomotor shaft 202. The flux goes between stators 210 as shown in FIG. 16.Motor 200 may be considered to be a stacked motor in that a plurality ofstators 210 are used in rotating rotor 236 and motor shaft 202.Increased power is provided by such a stacking arrangement. Such acombination of a single rotor and two (2) stators can be used as thebasic building block of a larger, more highly stacked motor.

FIGS. 17 and 18 illustrate one such more highly stacked motor 300, whichis made up of two (2) pair of stators 310. Two (2) rotors 336, each ofwhich is located between the stators 310 of a different pair of stators,are provided. Both of the rotors 336 are attached to shaft 302.

Each of the stators 210 and 310 has substantially the same configurationas stator 10, previously described. Also, each of the rotors 236 and 336has substantially the same configuration as the rotor 136, previouslydescribed, except that rotors 231 include no region (corresponding toregion 161) with the magnetic properties of a soft magnetic material.

Each pair of stators 310 of motor 300 is independent of the other statorpair. The flux can either go through the back to back stators 310 ofmotor 300 or can be directed within each pair of stators 310, as shownin FIG. 18.

The stacked motors 200 and 300 can be used in any application in whichthe rotation of motor shaft 202 and 302, respectively, is to betranslated into useful work. Stacked motors 200 and 300 can becontrolled using conventional control electronics, shown schematicallyat 204 and 304, respectively. Control electronics 204 and 304communicate with each of the stators 210 and 310, respectively, toenergize the windings located on each of these stators. Energizing thewindings on stators 210 and 310 causes the rotors 236 and 336,respectively, and motor shafts 202 and 302, respectively, to rotate. Theother end of each of the motor shafts 202 and 302 may be secured to animplement, such as a pump, compressor, fan and the like, which isoperated by the power transmitted by the shaft.

The present stators, and dynamo electric machines and pumps includingsuch stators, provide substantial benefits whether a single stator androtor are employed or a plurality of stators and/or rotors are employed.These stators, which include a mass of pressed metal particles,preferably provide for enhanced power generation, for example, relativeto a similar dynamo electric machine employing a stator including asolid metal mass or member in place of a mass of pressed metalparticles. Such enhanced power generation can result in reduced machinesize and/or increased overall power generation so that the dynamoelectric machines including such stators advantageously can be used in abroader range of applications including heavy duty or power intensiveapplications. The present stators represent a substantial improvementrelative to conventional stators, particularly because of the enhancedpower generating capabilities of dynamo electric machines including suchstators as well as the relatively straightforward and cost effective wayin which such stators can be produced.

While this invention has been described with respect to various specificexamples and embodiments, it is to be is understood that the inventionis not limited thereto and that it can be variously practiced within thescope of the following claims.

What is claimed is:
 1. A stator comprising: a plate configured to besubstantially flat and having a first end surface, a substantiallyopposing second end surface and a peripheral surface therebetween; aplurality of spaced apart projections starting at the peripheral surfaceand extending from said second end surface away from said plate anddefining a plurality of slots therebetween, said slots having a widthdefined as a distance between two successive projections, and a lengthorthogonal to the slot width; and a plurality of magnetic windingspositioned around said projections and substantially orthogonal to theslot length, said plate and said projections comprising a mass of metalparticles, said stator being included in a brushless direct currentelectric motor comprising a rotor including a single sided generallyflat array of a plurality of permanent magnetic poles.
 2. The stator ofclaim 1 wherein said plate and said projections comprising a mass ofmetal particles has a density equal to at least about 95% of thetheoretical density of a solid metal mass.
 3. The stator of claim 1wherein said plate has a central axis which intersects both said firstend surface and said second end surface, and said plurality ofprojections each extend inwardly from said peripheral surface andterminate prior to intersecting said central axis.
 4. The stator ofclaim 3 wherein the width of each slot is substantially constant betweenthe two projections which define the slot.
 5. The stator of claim 1wherein substantially all of the plurality of windings are positionedaround the projections substantially parallel to the first end surfaceof the plate.
 6. A dynamo electric machine comprising: a rotor having arotary axis, and including a single sided generally flat array of aplurality of permanent magnetic poles; and a stator spaced apart fromand generally facing said single sided generally flat array, said statorincluding a first end surface, a second end surface, a peripheralsurface therebetween, a length extending from said first end surface tosaid second end surface, and a plurality of spaced apart projectionsstarting at the peripheral surface and extending from said second endsurface away from said first end surface toward said rotor and defininga plurality of slots therebetween, said slots having a length parallelto the length between the first and second end surface, and said statorhaving a plurality of magnetic windings positioned around saidprojections and substantially nonparallel to the length of said slots,said magnetic windings being adapted to effect rotation of said rotorabout said rotary axis upon energization thereof, said stator comprisinga mass of metal particles, the dynamo electric machine being a brushlessdirect current motor.
 7. The dynamo electric machine of claim 6 whereinthe machine is a brushless direct current electric motor configured toproduce reduced eddy current effects during operation of said motorrelative to the operation of a substantially identical dynamo electricmachine in which a solid metal mass is used in place of the mass ofmetal particles.
 8. The dynamo electric machine of claim 6 which furthercomprises a work component coupled to and rotatable with said rotor. 9.The dynamo electric machine of claim 6 wherein each of said slots havinga substantially constant dimension between the two projections whichdefine the slot.
 10. An apparatus for performing useful work comprising:a work component having a rotary axis and being mounted for rotationabout said rotary axis, said work component being configured andpositioned so that the rotation of said work component is effective toperform work on a material in contact with said work component; a rotorcoupled to and rotatable with said work component, and including asingle sided generally flat array of a plurality of permanent magneticpoles; and a stator spaced apart from and generally facing said singlesided generally flat array, said stator including a plurality of spacedapart projections starting at a peripheral surface of the stator anddefining a plurality of slots therebetween, each of said slots having alength orthogonally oriented relative to a distance between twoprojections defining the slot, and said stator having a plurality ofmagnetic windings positioned around said projections and substantiallynonparallel to the length of said slots, said magnetic windings beingadapted to effect rotation of said rotor and said work component uponenergization thereof by direct electric current, said stator comprisinga mass of metal particles.
 11. The apparatus of claim 10 wherein saidstator comprising a mass of metal particles has a density equal to atleast about 95% of the theoretical density of a solid metal mass. 12.The apparatus of claim 10 wherein reduced eddy current effects areobtained during operation relative to the operation of a similarapparatus in which a solid metal mass is used in place of the mass ofmetal particles in the stator.
 13. The apparatus of claim 10 whichcomprises at least one of a plurality of said stators and a plurality ofrotors.
 14. The apparatus of claim 10 wherein said stator includes aplate configured to be substantially flat and having a first endsurface, a substantially opposing second end surface and a peripheralsurface therebetween, and the plurality of spaced apart projectionsextend from said second end surface away from said plate toward saidrotor.
 15. The apparatus of claim 14 wherein each of said slots having asubstantially constant dimension between the two projections whichdefine the slot.
 16. A pump comprising: a pump casing having an inletand an outlet; an impeller having a rotary axis and being rotatablymounted within said pump casing for rotation about said rotary axis,said impeller being configured and positioned relative to said pumpcasing so that the rotation of said impeller is effective to urge fluidfrom said inlet to flow through said outlet; a rotor coupled to androtatable with said impeller, and including a single side generally flatarray of a plurality of permanent magnetic poles; and a stator spacedapart from and generally facing said single sided generally flat array,said stator including a plurality of spaced apart projections startingat a peripheral surface of the stator and defining a plurality of slotstherebetween, each of said slots having a length orthogonally orientedrelative to a distance between two projections defining the slot, andsaid stator having a plurality of magnetic windings positioned aroundsaid projections and substantially nonparallel to the length of saidslots, said magnetic windings being adapted to effect rotation of saidrotor and said impeller upon energization thereof by direct electricalcurrent, said stator comprising a mass of metal particles.
 17. The pumpof claim 16 wherein said stator comprising a mass of metal particles hasa density equal to at least about 95% of the theoretical density of asolid metal mass.
 18. The pump of claim 16 wherein reduced eddy currenteffects are obtained during operation relative to the operation of asimilar pump in which a solid metal mass is used in place of the mass ofmetal particles in the stator.
 19. The pump of claim 16 which comprisesat least one of a plurality of said stators and a plurality of saidrotors.
 20. The pump of claim 16 wherein said stator includes a plateconfigured to be substantially flat and having a first end surface, asubstantially opposing second end surface and a peripheral surfacetherebetween, and the plurality of spaced apart projections extend fromsaid second end surface away from said plate toward said rotor.
 21. Thepump of claim 20 wherein each of said slots having a substantiallyconstant dimension between the two projections which define the slot.